1. Field of the Invention
The present invention relates mainly to very large sand bags which are used, for example, for irrigation works or river-improvement works, slope face reinforcement or retaining wall constructions, accretion for roads or buildings, reclamation works, and natural disaster restoration works. In particular, the invention relates to a shape-retention-type hoisting rectangular parallelepiped bag which requires only one hanging mechanism for execution of works while maintaining a stable, easy-to-pile shape when a plurality of rectangular parallelepiped sand bags are stacked one on another for use. The invention further relates to a bag which can be employed in combination with a sandbag involved construction method that employs small sand bags, and which allows execution of works to cover a large area at one time, thereby providing improved work efficiency. Furthermore, another aspect of the inventive bag or its rectangular shape can also be utilized to carry grain-shaped substances such as wheat or soybeans in the bag, allowing for loading goods or placing stocks with improved efficiency. This improvement can be seen when compared to conventional sand bags which typically have a cylindrical shape or an inverted balloon (or a cloth bag tightly closed at its open end), thus causing gaps between the sand bags.
2. Description of Related Art
Sand bags are piled up or stacked in layers for use in irrigation works or river-improvement works and restoration works from natural disasters caused by, for example, typhoon or heavy rain. Conventional sand bags are prepared, as shown in FIG. 13, in a manner such that a sand bag 101 of high durability, such as hempen bags or polyethylene or polypropylene bags or meshed bags, is filled with soil, and the opening of the bag is closed with Velcro closure (registered trade mark) 105 or the like. Typical larger sand bags for construction works may weigh one ton or greater, so that those sand bags are carried using crane trucks or backhoes. As shown in FIG. 14, a plurality of sand bags 101 are often stacked in layers for restoration works from natural disaster caused by typhoon or heavy rain.